Projection-type display device

ABSTRACT

A rear-type projection display device is provided, in which even a liquid crystal panel having several point defects is used, the point defects are hardly recognized. According to the present invention, in order not to display the display defects (the bright spots or unlit defects) that take place when a light from a light source transmits a liquid crystal panel having the point defects, means for correcting the display defects is provided on the liquid crystal panel side of a screen.

This application is a continuation of U.S. application Ser. No.09/569,727, filed on May 10, 2000, now U.S. Pat. No. 6,305,806, which isa continuation of U.S. application Ser. No. 09/159,831, filed on Sep.24, 1998, now U.S. Pat. No. 6,109,753 issued Aug. 29, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a picture display device that utilizesso-called electrooptical materials or electrooptical elements, such asliquid crystal, optical characteristics of which are subject tomodulation by voltage, current, frequency or other electrical factors,and more particularly to a projection-type display device in which adisplay device provided with electrical elements such as transistors forcontrolling pixels for every pixel is used.

2. Description of the Related Art

As a projection system for projection-type display devices, there hasbeen known a method called a rear projection system. In the rearprojection system, an image is formed on the surface of a transmissiontype diffusion screen (hereinafter it is sometimes referred to as simplya screen) through a light source, enabling the image to be observed fromthe screen surface side opposite to the light source. A conventionaldevice is shown in FIG. 5A. In FIG. 5A, reference numeral 500 denotes amain body; 501, a light source; 502, a liquid crystal panel and opticalsystem; 503 and 504, mirrors; and 505, a screen.

Such display device of projection type (hereinafter it is sometimesreferred to as a rear projection-type display device) irradiates asmall-sized liquid crystal panel of 3 inch or less with an intense lightfrom the light source to display an enlarged image on the screen byutilizing the optical system. For that reason, in order to make thedisplay screen high in fineness and density, it is necessary further tonarrow intervals between pixels of the liquid crystal panel or to reducethe size of the pixels and wirings themselves.

As indicated above, the development of highly fine liquid crystal panelsis keenly attempted to obtain the display screen with high fineness andhigh density.

However, when the number of dot of the liquid crystal panel (the numberof pixel) is increased to make the screen high in fineness, the linedefect, point defect or the like tend to take place causing low yield.The term “point defect” means one pixel or an aggregate of more pixelswhich are malfunctioned by some reasons. Bright spots in which a whitedot is displayed at the time of displaying black and unlit defects inwhich a black dot is displayed at the time of displaying white are maindisplay malfunctions caused by the point defect.

That is especially the case with the projection-type display device inwhich the small-sized liquid crystal panel is irradiated with an intenselight and an enlarged image is displayed on the screen using the opticalsystem. Accordingly, upon use of the liquid crystal panel having atleast one point defect, the bright spot 508 is displayed when displayingblack, as shown in FIG. 5B, and the unlit defect 509 is also displayedwhen displaying white, as shown in FIG. 5C which make the displaymalfunctions prominent.

There is known a method in which the liquid crystal panel is processedwith a laser beam to repair the panel, or the like. As means forrepairing such point defects, however, the liquid crystal panel of theprojection type is difficult to be thus processed minutely because thepixel pitch or the like is very small. Accordingly, the repair thereofis seems to become difficult when the fineness of the panel is furtherenhanced.

SUMMARY OF THE INVENTION

In view of the foregoing problems, an object of the present invention isto provide a rear projection-type display device with that the pointdefect is hardly recognized in the eyes of an observer and good displayquality is obtained even when a liquid crystal panel having severalpoint defects is used.

In an arrangement of the present invention disclosed in thisspecification, a projection-type display device is comprised of: a lightsource; an electrooptical element that modulates a light from the lightsource; a screen; optical means for projecting the light modulated bythe electrooptical element on the screen; and correction means forcorrecting the display malfunction on the screen due to the point defectof the electrooptical element.

In the above arrangement, the correction means is one selected fromlight-shielding means, light scattering means, light reflecting means,light collecting means and light absorbing means, or the combinationthereof.

In the above arrangement, the correction means is provided adjacent tothe rear surface side of the screen.

In the above arrangement, the correction means is provided on the rearsurface of the screen.

In the above arrangement, the correction means is means formed byprocessing the screen to reduce an amount of transmitted light throughthe screen

In the above arrangement, the means for collecting the light is aprotrusion in the shape of cone, elliptical hemisphere or planoconvex,and has function of a lens.

In the present invention, the screen is composed of a light transmittingplate that is mainly formed of a transparent material and on the rearsurface side of the screen, as shown in FIG. 1, the correction means forcorrecting the display malfunction is provided.

Note that the term “screen” appeared in this specification means asurface on which an observer can confirm the display quality (displayingplane), and a back-side surface thereof is called the rear surface ofthe screen.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is more readily understood by means ofaccompanying drawings, in which:

FIG. 1 is a block diagram showing a first embodiment of the presentinvention;

FIG. 2 is a block diagram showing a second embodiment of the presentinvention;

FIGS. 3A to 3C are enlarged views showing correction means in accordancewith the present invention;

FIG. 4 is a schematic view of a liquid crystal panel and optical system;and

FIGS. 5A to 5C are views showing an example of a conventional device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinbelow, descriptions will successively be made of embodimentsaccording to the present invention with reference to the drawings.

[Embodiment 1]

FIG. 1 is a block diagram showing an embodiment of the presentinvention.

In FIG. 1, a light source 101 employs a metal halide lamp. The lightsource 101 is, however, not particularly limited to the metal halidelamp as long as it is a white light lamp. A liquid crystal panel andoptical system 102 shown in FIG. 1 is comprised of, as shown in FIG. 4as an example, a cross dichroic prism 403 for separating a light fromthe light source 401 into three colored lights different from each other(red, blue, green) to outgo the same, a polarized beam splitter 406 forrespectively converging the lights separated into three colors, a totalinternal reflection mirror 404, a polarizing plate 405 and three liquidcrystal panels 400. What denoted by reference numeral 102 in FIG. 1correspond to the 402 in FIG. 4. The liquid crystal panel and opticalsystem 102 is not limited particularly as long as it is a liquid crystalpanel and optical system of rear projection type. Also, though not shownin the figures, as the other optical system such an arrangement may beemployed in which a light collecting lens is disposed between the lightsource and the liquid crystal panel, or a projecting lens or the like isdisposed between the liquid crystal panel and a screen 105.

The lights of three colors from the cross dichroic prism 403 arerespectively irradiated onto different liquid crystal panels from eachother to synthesize each image obtained on the respective liquid crystalpanels by the polarized beam splitter 406. Thereafter, each one isirradiated while being enlarged on the screen so that an image isobtained. The color display is thus attained without provision of acolor filter.

The screen 105 is mainly formed of a light transmitting plate made of atransparent material. In the rear surface thereof, a light-shieldingobject 106 is provided as shown in FIG. 1.

When black display is conducted on the screen so that bright spots aredeveloped, the location where the light-shielding object is to beprovided is a portion where the bright spots present. Thelight-shielding object 106 is provided in order to prevent the lightthat passes through the point defect of the liquid crystal panel fromtraveling in a direction in which an observer gazes at the screen.

In this embodiment, a colored film, for instance, a black film or bluefilm is employed as the light-shielding object. This light-shieldingobject 106 is not limited particularly as far as it is a material thatreduces the amount of transmitted light through the screen.

Accordingly, the light-shielding object may he made up of a film thatreflects a light completely. For example, a metal material that reflectsa light completely may be used. Alternatively, a colored layer may beprovided by applying a solution containing a pigment only to the portionat which bright spots are developed.

As shown in FIG. 3A, an arrangement in which a concave 306 is formed ona screen 305 itself may be also employed to scatter the light. And also,as shown in FIG. 3B, an arrangement in which a portion 316 is provided,which is obtained by transforming or discoloring a screen 315 itself forthe purpose of reducing the amount of transmitted light may be employed.

When white display is conducted on the screen so that the unlit defectsare developed, though not shown in the figures, a light collectingobject is provided on the rear surface of the screen in a similar manneras in the case of the black display. The portion where the lightcollecting object is provided is a portion in which the unlit defectsare developed. The light collecting object collects the light to shadethe unlit defects.

In this embodiment, a lens with a shape of elliptical hemisphere asshown in FIG. 3C is used as the light collecting object. The lightcollecting object may have a shape of cone or planoconvex. The lightcollecting object is not limited particularly as far as it is a materialthat collects the light of the screen.

In this embodiment, mirrors 103 and 104 are provided so that the lightsemitted from the liquid crystal panel are reflected to enter to thescreen. The mirrors refract an optical path from the liquid crystalpanel to the screen, which shortens the depth of the whole device,thereby capable of downsizing the same.

In this embodiment, the display defects (the bright spots or unlitdefects) caused by portions of the point defects of the liquid crystalpanel were hardly recognized and an excellent image was obtained.

That correction method is preferable to be applied to all of the pointdefects of the liquid crystal panel. Also, the method can be appliedonly to the point defects of green, which are readily recognized. As aresult, a high improving effect can be obtained.

[Embodiment 2]

A light-shielding object or a light collecting object is provideddirectly on a screen in Embodiment 1. In the present embodiment, asubstrate having a transparency or a filter having a transparency isarranged in contact with the screen. The light-shielding object or thelight collecting object is provided via the substrate or the filterabove.

In FIG. 2, a xenon lamp is employed as a light source 201. A liquidcrystal panel and optical system 202 similar to the ones used inEmbodiment 1 is used. That is, the liquid crystal panel and opticalsystem 202 in FIG. 2 corresponds to the 402 in FIG. 4. As the opticalsystem, though not shown, an arrangement in which a light collectinglens is provided between the light source and the liquid crystal panel,or an arrangement in which a projecting lens is provided between theliquid crystal panel and a screen 205 may be employed. In thisembodiment, the liquid crystal panel and the optical system 202 is,similarly to Embodiment 1, not particularly limited as long as it is arear projection-type liquid crystal panel and optical system.

The screen 205 is mainly formed of a light transmitting plate made of atransparent material. The rear surface thereof is provided with asubstrate having a transparency in contact with the screen or a filterhaving a transparency in contact with the screen, which is denoted byreference numeral 207 in FIG. 2, and on which the light-shielding objector the light collecting object is disposed.

With the above arrangement, may be The light-shielding object or thelight collecting object is readily formed through the aid of thesubstrate or filter 207. Also, if the liquid crystal panel is brokenfrom some reason, the device may be repaired at low price by replacingthe substrate or filter 207 on which a light-shielding object 206 or thelight collecting object is provided as well as replacing the liquidcrystal panel.

Similarly to Embodiment 1, the display defects (the bright spots orunlit defects) due to portions of the point defects of the liquidcrystal panel were hardly recognized and an excellent image could beobtained also in this embodiment.

[Embodiment 3]

In the present embodiment, a halogen lamp is employed as a light source.The light source is not limited particularly as long as it is a whitelamp. One liquid crystal panel with a color filter is utilized toconstitute a transmission-type liquid crystal display device. Also,though not shown in the figure, an arrangement for an optical system maybe such that a light collecting lens is provided between the lightsource and the liquid crystal panel, or that a projecting lens isdisposed in the front surface of the liquid crystal panel.

As in Embodiment 1 or 2, in order not to display the display defects(the bright spots or unlit defects) due to portions of the point defectswhich take place when the light from the light source is transmittedthrough a liquid crystal panel having the point defects, correctionmeans for correcting the display defects by the point defects isprovided on the screen, or on the filter disposed in contact with thescreen or the rear surface side of the substrate provided in contactwith the screen.

Similarly to Embodiments 1 and 2, the display defects (the bright spotsor unlit defects) due to portions of the point defects of the liquidcrystal panel were hardly recognized and an excellent image could beobtained in this embodiment, too.

[Embodiment 4]

It is needless to say that the present invention is not limited to theprojection-type display devices that are shown in Embodiments 1 to 3.Application range of the present invention is quite so wide that it isapplicable to every projection-type display device. For example, thepresent invention can be applied to a projection-type display device inwhich liquid crystal display elements, EL (electro luminescence)elements, EC (electro chrominance) elements, PDP elements and otherspontaneous luminescent elements are used. In particular, the presentinvention is extremely effective when applied to a device that employs aminute small-sized liquid crystal panel which is difficult to fabricateand low in the yield.

According to the present invention, in order not to display the displaydefects (the bright spots or unlit defects) that take place when thelight from the light source transmits the liquid crystal panel havingthe point defects, means for correcting the display defect is providedadjacent to the rear surface side or on the rear surface of the screen.As a result, thus, an excellent picture is provided to an observer.

With an application of the present invention, the liquid crystal panelhaving the point defects which has been not allowed to be used in therear projection-type display device can be sufficiently used as a goodarticle, whereby the yield can be improved.

What is claimed is:
 1. A projection-type display device comprising: ascreen, said screen enabling an image to be observed from a screensurface side; at least an electro luminescence element; and a lightshielding object preventing a point defect of the an electroluminescence element from being observed on the screen when a blackimage is displayed on the screen.
 2. A projection-type display deviceaccording to claim 1, wherein the light shielding object includes alight reflecting film.
 3. A projection-type display device according toclaim 1, wherein the light shielding object comprises a metal material.4. A projection-type display device according to claim 1, wherein atransparent object is provided over a rear surface of the screen.
 5. Aprojection-type display device according to claim 4, wherein thetransparent object comprises one selected from the group consisting of atransparent substrate and a transparent filter.
 6. A projection-typedisplay device according to claim 1, wherein the screen comprises alight transmitting plate.
 7. A projection-type display device accordingto claim 1, wherein the screen surface side is opposite to said electroluminescence element.
 8. A projection-type display device according toclaim 1, wherein the light shielding object includes a colored film. 9.A projection-type display device according to claim 8, wherein thecolored film comprises a pigment.
 10. A projection-type display deviceaccording to claim 8, wherein said colored film reduces an amount oftransmitted light of said screen.
 11. A projection-type display deviceaccording to claim 1, wherein light shielding object is provided overthe rear surface side of said screen.
 12. A projection-type displaydevice according to claim 1, further comprising an optical system forprojecting the image to be observed onto the screen.
 13. Aprojection-type display device according to claim 1, wherein saidoptical system includes at least a cross dichroic prism.
 14. Aprojection-type display device according to claim 1, wherein saidprojection type display device is a rear projection type display device.15. A projection-type display device according to claim 1, wherein atransparent object is in contact with a rear surface of the screen. 16.A projection-type display device comprising: a screen, said screenenabling an image to be observed from a screen surface side; at least anelectro luminescence element; and a light collecting object preventing apoint defect of the electro luminescence element from being observed onthe screen when a white image is displayed on the screen.
 17. Aprojection-type display device according to claim 16, wherein the lightcollecting object has a lens with a shape of a cone.
 18. Aprojection-type display device according to claim 16, wherein the lightcollecting object has a lens with a shape of a planoconvex.
 19. Aprojection-type display device according to claim 16, wherein the lightcollecting object has a lens with a shape of an elliptical hemisphere.20. A projection-type display device according to claim 16, wherein atransparent object is provided over a rear surface of the screen.
 21. Aprojection-type display device according to claim 16, further comprisingan optical system for projecting the image to be observed onto thescreen.
 22. A projection-type display device according to claim 16,wherein the screen surface side is opposite to said electro luminescenceelement.
 23. A projection-type display device according to claim 16,wherein the light collecting object has a lens.
 24. A projection-typedisplay device according to claim 20, wherein the transparent objectcomprises one selected from the group consisting of a transparentsubstrate and a transparent filter.
 25. A projection-type display deviceaccording to claim 16, wherein said projection type display device is arear projection type display device.
 26. A projection-type displaydevice according to claim 16, wherein said light collecting object isprovided over the rear surface side of said screen.
 27. Aprojection-type display device according to claim 16, wherein the screencomprises a light transmitting plate.
 28. A projection-type displaydevice according to claim 21, wherein said optical system includes atleast a cross dichroic prism.
 29. A projection-type display deviceaccording to claim 16, wherein a transparent object is in contact with arear surface of the screen.
 30. A projection-type display devicecomprising: an electro luminescence element; a screen for displaying animage of said electro luminescence element; and means for correcting adisplay malfunction on the screen caused by a point defect of saidelectro luminescence element, said means provided over a portion of thescreen.
 31. A projection-type display device according to claim 30,wherein said means is a light shielding object.
 32. A projection-typedisplay device according to claim 30, wherein said means is a lightscattering object.
 33. A projection-type display device according toclaim 30, wherein said means is a light reflecting object.
 34. Aprojection-type display device according to claim 30, wherein said meansis a light collecting object.
 35. A projection-type display deviceaccording to claim 30, wherein said means is a light absorbing object.36. A projection-type display device according to claim 35, wherein saidlight absorbing object reduces an amount of transmitted light of saidscreen.
 37. A projection-type display device according to claim 30,wherein the screen comprises a light transmitting plate.
 38. Aprojection-type display device according to claim 30, wherein atransparent object is in contact with a rear surface of the screen. 39.A projection-type display device according to claim 30, wherein thetransparent object comprises one selected from the group consisting of atransparent substrate and a transparent filter.
 40. A projection-typedisplay device according to claim 30, wherein the screen surface side isopposite to said electro luminescence element.
 41. A projection-typedisplay device according to claim 33, wherein the light reflectingobject includes a metal material.
 42. A projection-type display deviceaccording to claim 34, wherein the light collecting object comprises alens with a shape of elliptical hemisphere, cone, or planoconvex.
 43. Aprojection-type display device according to claim 34, wherein the lightcollecting object comprises a lens.
 44. A projection-type display deviceaccording to claim 35, wherein the light absorbing object comprises acolored film.
 45. A projection-type display device according to claim44, wherein the colored film comprises a pigment.
 46. A projection-typedisplay device according to claim 30, further comprising an opticalsystem for projecting the image to be observed onto the screen.
 47. Aprojection-type display device according to claim 46, wherein saidoptical system comprises a cross dichroic prism.
 48. A projection-typedisplay device according to claim 30, wherein said projection typedisplay device is a rear projection type display device.
 49. Aprojection-type display device according to claim 30, wherein atransparent object is provided over a rear surface of the screen.
 50. Aprojection-type display device comprising: a screen, said screenenabling an image to be observed from a screen surface side; at least aPDP element; and a light shielding object preventing a point defect ofthe PDP element from being observed on the screen when a black image isdisplayed on the screen.
 51. A projection-type display device accordingto claim 50, wherein the light shielding object comprises a lightreflecting film.
 52. A projection-type display device according to claim50, wherein the light shielding object comprises a metal material.
 53. Aprojection-type display device according to claim 50, wherein atransparent object is in contact with a rear surface of the screen. 54.A projection-type display device according to claim 53, wherein thetransparent object comprises one selected from the group consisting of atransparent substrate and a transparent filter.
 55. A projection-typedisplay device according to claim 50, wherein the screen comprises alight transmitting plate.
 56. A projection-type display device accordingto claim 50, wherein the screen surface side is opposite to said PDPelement.
 57. A projection-type display device according to claim 50,wherein the light shielding object comprises a colored film.
 58. Aprojection-type display device according to claim 57, wherein thecolored film comprises a pigment.
 59. A projection-type display deviceaccording to claim 50, wherein said light shielding object is providedover a rear surface side of said screen.
 60. A projection-type displaydevice according to claim 50, further comprising an optical system forprojecting the image to be observed onto the screen.
 61. Aprojection-type display device according to claim 60, wherein saidoptical system includes at least a cross dichroic prism.
 62. Aprojection-type display device according to claim 50, wherein saidprojection-type display device is a rear projection type display device.63. A projection-type display device according to claim 50, wherein saidcolored film reduces an amount of transmitted light of said screen. 64.A projection-type display device according to claim 50, wherein atransparent object is provided over a rear surface of the screen.
 65. Aprojection-type display device comprising: a screen, said screenenabling an image to be observed from a screen surface side; at least aPDP element; and a light collecting object preventing a point defect ofthe PDP element from being observed on the screen when a white image isdisplayed on the screen.
 66. A projection-type display device accordingto claim 65, wherein the light collecting object comprises a lens with ashape of a cone.
 67. A projection-type display device according to claim65, wherein the light collecting object comprises a lens with a shape ofa planoconvex.
 68. A projection-type display device according to claim65, wherein the light collecting object comprises a lens with a shape ofan elliptical hemisphere.
 69. A projection-type display device accordingto claim 65, wherein a transparent object is provided over a rearsurface of the screen.
 70. A projection-type display device according toclaim 65, further comprising an optical system for projecting the imageto be observed onto the screen.
 71. A projection-type display deviceaccording to claim 65, wherein the screen surface side is opposite tosaid PDP element.
 72. A projection-type display device according toclaim 65, wherein the light collecting object comprises a lens.
 73. Aprojection-type display device according to claim 69, wherein thetransparent object comprises one selected from the group consisting oftransparent substrate and a transparent filter.
 74. A projection-typedisplay device according to claim 65, wherein said projection-typedisplay device is a rear projection type display device.
 75. Aprojection-type display device according to claim 65, wherein the screencomprises a light transmitting plate.
 76. A projection-type displaydevice according to claim 70, wherein said optical system includes atleast a cross dichroic prism.
 77. A projection-type display deviceaccording to claim 65, wherein said light collecting object is providedover the rear surface of said screen.
 78. A projection-type displaydevice according to claim 65, wherein a transparent object is in contactwith a rear surface of the screen.
 79. A projection-type display devicecomprising: a PDP element; a screen for displaying an image of said PDPelement; and means for correcting a display malfunction on the screencaused by a point defect of said PDP element, said means provided over aportion of the screen.
 80. A projection-type display device according toclaim 79, wherein said means is a light shielding object.
 81. Aprojection-type display device according to claim 79, wherein said meansis a light scattering object.
 82. A projection-type display deviceaccording to claim 79, wherein said means is a light reflecting object.83. A projection-type display device according to claim 79, wherein saidmeans is a light collecting object.
 84. A projection-type display deviceaccording to claim 79, wherein said means is a light absorbing object.85. A projection-type display device according to claim 84, wherein saidlight absorbing object reduces an amount of transmitted light of saidscreen.
 86. A projection-type display device according to claim 79,wherein the screen comprises a light transmitting plate.
 87. Aprojection-type display device according to claim 79, wherein atransparent object is in contact with a rear surface of the screen. 88.A projection-type display device according to claim 79, wherein thetransparent object comprises one selected from the group consisting of atransparent substrate and a transparent filter.
 89. A projection-typedisplay device according to claim 79, wherein the screen surface side isopposite to said PDP element.
 90. A projection-type display deviceaccording to claim 82, wherein the light reflecting object includes ametal material.
 91. A projection-type display device according to claim93, wherein the light collecting object comprises a lens with a shape ofelliptical hemisphere, cone, or planoconvex.
 92. A projection-typedisplay device according to claim 83, wherein the light collectingobject comprises a lens.
 93. A projection-type display device accordingto claim 84, wherein the light absorbing object comprises a coloredfilm.
 94. A projection-type display device according to claim 93,wherein the colored film comprises a pigment.
 95. A projection-typedisplay device according to claim 79, further comprising an opticalsystem for projecting the image to be observed onto the screen.
 96. Aprojection-type display device according to claim 95, wherein saidoptical system comprises a cross dichroic prism.
 97. A projection-typedisplay device according to claim 79, wherein said projection typedisplay device is a rear projection type display device.
 98. Aprojection-type display device according to claim 79, wherein said meansis provided over the rear surface side of the screen.
 99. Aprojection-type display device according to claim 89, wherein atransparent object is provided over a rear surface of the screen.